1. Field of the Invention
The invention relates to a rubber sleeve having an inner carrier sleeve which can be expanded by means of air, at least one compressible layer arranged over the carrier sleeve, and an outer covering layer. A similar device is disclosed in U.S. Pat. No. 6,148,725.
2. Description of the Related Art
Sleeves of this type are disclosed, for example, by U.S. Pat. Nos. 5,429,048, 5,323,702, 5,440,981 and 5,304,267. One disadvantage of these known rubber cylinder sleeves (transfer cylinder sleeves) is that the middle and lower layers of the same have to be at least partly continuous. This has a particularly detrimental effect on the production costs.
In addition, U.S. Pat. No. 5,351,615 discloses the practice of applying a rubber blanket to a carrier plate, for example by adhesive bonding. After this, this arrangement is shaped into a rubber cylinder sleeve and the mutually facing ends of the carrier plate and those of the rubber blanket or rubber covering are joined to each other, for example by welding or adhesive bonding. Although this arrangement no longer has a gap, a joining seam or a joint location remains on the surface.
In the rubber cylinder sleeve shown in U.S. Pat. No. 5,429,048, its outer layer is continuously sleeve-like and consists of an incompressible material. Apart from the higher production costs already mentioned, a continuous outer layer has the disadvantage that, during rolling contact with a plate cylinder and an impression cylinder, the rubber blanket sleeve is loaded with tangential forces to which further forces are added with each revolution. High loading on the rubber blanket sleeve is established. This loading also has a detrimental effect on the printing quality (for example by a tendency to slippage of the rubber blanket sleeve in relation to the web to be printed. in the press nip, and in the rolling nip with a plate cylinder).
It is an object of the present invention to produce a genus-forming rubber cylinder sleeve, especially for web-fed rotary offset printing machines, more cheaply as compared with the known sleeves of this type, with approximately the same or improved printing quality and behaviour.
The object is achieved by designing the covering layer as a finite layer having a joint location which is filled with a compressible material. The rubber cylinder sleeve can be produced cost-effectively. In addition, it makes possible good printing quality since the joint location filled with compressible material is permitted to dissipate tangential forces during rolling contact with other printing-unit cylinders.
As is known from the prior art described above, the fundamental construction of such rubber cylinder sleeves substantially comprises an inner, preferably metallic sleeve. However, a glass-fibre reinforced (GRP) sleeve can also be used advantageously instead of the inner metal sleeve. The thickness of these sleeves is, for example, dimensioned in such a way that, when they are pushed onto the transfer cylinder, which is usually referred to as a rubber-covered cylinder, in printing machines operating in accordance with indirect printing processes, they can be expanded slightly by means of air. As shown in U.S. Pat. No. 5,429,048, such a sleeve can be pushed through the side wall of a printing machine onto the transfer cylinder previously exposed on one side. In the process, the sleeve to be pushed on is expanded with compressed air with the aid of openings provided in the transfer cylinder, so that fitting in a straightforward way is possible, after which, after the compressed air has been removed, the sleeve pushed on assumes a firm seat on the transfer cylinder.
At least one further layer which is compressible, i.e. having air inclusions, is appliedxe2x80x94directly or indirectlyxe2x80x94to this inner, preferably metallic carrier sleeve. At least one covering layer which, for example, can consist of an elastomeric material, is provided above this compressible layer. Using this material, the image to be printed is accepted from a printing plate, for example an offset printing plate or a sleeve-like offset printing plate, and is transferred to a printing medium.
A further non-expandable layer is preferably provided between the compressible layer (e.g. an elastomer with air inclusions) and the covering layer, for example in the form of a hard elastomeric material or, for example, in the form of short fibres (e.g. threads) which can also be embedded in the hard elastomeric material. Alternatively, a non-expandable layer or non-expandable particles, such as threads or pieces of threads, can also be introduced directly into the aforementioned volume-compressible layer.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.